Code division multiple access enhanced capacity system

ABSTRACT

A code division multiple access (CDMA) communication system using spread spectrum signaling over a communication bandwidth uses two different signal spectra generated using two different respective spreading code formats, such as NRZ code formatting and staggered Manchester code formatting, for respectively providing nonsplit spectra having a center peak and split spectra having a center null. The spectra are combined during transmission as a CDMA communication signal having a composite spectrum. The use of different code formats produces the composite spectrum of respective center peak and center null spectra that enables increased channel capacity.

STATEMENT OF GOVERNMENT INTEREST

The invention was made with Government support under contract No.F04701-00-C-0009 by the Department of the Air Force. The Government hascertain rights in the invention.

FIELD OF THE INVENTION

The invention relates to the field of code division multiple accesscommunications systems. More particularly the present invention relatesto concurrent code formatting of spreading codes in differing formatsfor use in code division multiple access communications systems forincreased channel capacity.

BACKGROUND OF THE INVENTION

Code division multiple access (CDMA) communications have been used forsome time. Typically, transmitted data is formatted and the spectrum isspread using CDMA spreading codes for communicating CDMA spread spectrumcommunication signals between a transmitter and a plurality of receiverswithin a null-to-null communications bandwidth. A transmitted signalincludes superimposed spread spectrum signals spread by respectivespreading codes for providing code division access to multiplereceivers. Differing spreading codes provide signal code divisionmultiplexing for enabling the respective receivers to acquire particularrespective communication spread spectrum signals among all of thetransmitted spread spectrum signals of the transmitted signal. The CDMAcommunication systems use a particular digital format to format a datastream prior to spectrum spreading and prior to transmission. Thedigital format is also applied to the spreading codes prior to spreadingformatted data. One such digital format is the nonreturn to zero (NRZ)format. Another format is the Manchester format, also known asbiphase-L. In an NRZ CDMA communication system, an NRZ format is used toformat separate data streams into NRZ formatted data streams that arethen spectrum spread by respective NRZ formatted CDMA spreading codesfor transmission to respective receivers. The communication spectrum ofan NRZ formatted and spread spectrum CDMA signal is characterized ashaving a center peak in the communications bandwidth. The communicationspectrum is also referred to as a nonsplit spectrum. In a ManchesterCDMA communication system, a Manchester format is used to format manyseparate data streams into Manchester formatted data streams that arethen spectrum spread by respective Manchester formatted CDMA spreadingcodes for transmission to respective receivers. The communicationspectrum of a Manchester formatted and spectrum spread CDMA signal ischaracterized as having a bandwidth center null of the communicationsbandwidth. This spectrum is also known as a split spectrum.

Typically, a CDMA system using NRZ formatting has a peak power spectraldensity at the center of the frequency band and is characterized as anonsplit spectrum signal. A CDMA system using Manchester code formattinghas a power spectral density null at the center of the frequency bandand is characterized as a split spectrum signal. Another availabledigital format is the binary offset carrier format that also provides asplit spectrum of a spread spectrum communication CDMA signal. Yetanother digital format that provides a split spectrum of a spreadspectrum communication CDMA signal is a staggered binary offset carrierformat. The binary offset carrier format, the staggered binary offsetcarrier format and the staggered Manchester format are specific cases ofthe generalized Manchester format. Conventional CDMA communicationsystems typically use NRZ code formatting. However, CDMA communicationsystems can also be implemented using a split spectrum code format, suchas the Manchester code digital format, staggered Manchester code format,the binary offset carrier digital format and the staggered binary offsetcarrier digital format. Manchester formats include all formatsformatting an digital input stream and produces a digital waveform thathas one for more transitions within a symbol time and that are centeredabout the center point of the symbol time, with a mean amplitude valueof zero. For examples, Biphase-L has one centered transition, staggeredBiphase-L has two symmetric transitions, binary offset carrier has morethan one transition, and staggered binary offset carrier has more thantwo transitions.

An NRZ CDMA communication system may, for example, have an availablebandwidth of 200 kHz and have a data rate of 400 bps. The spreading codechipping rate for the CDMA may be set at 100 kHz so that thenull-to-null bandwidth for the spectrum spread CDMA signal is 200 kHzwith a center peak. Channel capacity is the number of communicationchannels, that is, spread spectrum signals, which can be communicatedwithin a given bandwidth. Using NRZ formatting, the channel capacity isabout thirty-eight at a BER of 10⁻⁵. Channel capacity is a valuableresource. Increasing the channel capacity increases the number of usersthat can be served by a CDMA communication system. The NRZ, Manchester,staggered Manchester,binary offset carrier and staggered binary offsetcarrier formatted CDMA communication systems have limited channelcapacities. These and other disadvantages are solved or reduced usingthe invention.

SUMMARY OF THE INVENTION

An object of the invention is to provide increased channel capacity in acode division multiple access communication system.

Another object of the invention is to provide increased channel capacityin a code division multiple access communication system using aplurality of digital formats.

Yet another object of the invention is to provide increased channelcapacity in a code division multiple access communication system usingspectrum spreading by a pair of digital code formats providingrespective communication signal spectra.

Still another object of the invention is to provide increased channelcapacity in a code division multiple access communication system usingspectrum spreading by a pair of digital code formats respectivelyproviding a communication signal spectrum with a center null and acommunication signal spectrum with a center peak.

A further object of the invention is to provide increased channelcapacity in a code division multiple access communication system usingspectrum spreading with nonreturn to zero spreading code formattingproducing a communication signal spectrum with a center peak, and with ageneralized Manchester spreading code formatting producing acommunication signal spectrum with a center null.

Yet a further object of the invention is to provide increased channelcapacity in a code division multiple access communication systemproviding a composite communication spectrum produced by spectrumspreading with nonreturn to zero code formatting producing a nonreturnto zero communication spectrum having a center peak, and with ageneralized Manchester code formatting producing a generalizedManchester communication spectrum with a center null.

The invention is directed to a code division multiple accesscommunication (CDMA) system using spread spectrum signaling with atleast two different code formats producing different respectivecommunication signal spectra combined during transmission as atransmitted communication signal having a composite spectrum. A firstgroup of data streams is spectrum spread by a first group of spreadingcodes formatted using a first digital code format. A second group ofdata streams is spectrum spread by a second group of spreading codesformatted by a second digital code format. The formatted data streamsare spectrum spread by respective spread codes using two different codeformats. In the preferred form, nonreturn to zero (NRZ) code formattingand a generalized Manchester code formatting are used on respectivegroups of spreading codes for communicating over respectivecommunication channels. Using NRZ and a generalized Manchester codeformatting, nonsplit and split spectra are produced and superimposedover the communications bandwidth.

In the broad form of the invention, those communications channels havingspreading codes formatted by the first code format have a firstcommunication signal spectrum, and those communication channels havingspreading codes formatted by the second code format have a secondcommunication signal spectrum. The first and second communication signalspectra of the transmitted communication signal are superimposed duringtransmitter modulation to provide a composite communication signalspectrum of the superimposed first and second communication signalspectra. Using the two different digital code formats for formatting thefirst and second groups of spreading codes produces two differentcommunication signal spectra forming the composite communication signalspectrum that provides for increased channel capacity. These and otheradvantages will become more apparent from the following detaileddescription of the preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a dual spectrum code division multipleaccess (CDMA) transmitter.

FIG. 2 is a block diagram of a dual spectrum CDMA receiver.

FIG. 3 is a graph of the waveform components of the Manchester formattedsignal.

FIG. 4 is a graph of the waveform components of the staggered Manchesterformatted signal.

FIG. 5 is a graph of the power spectral densities of communicationspectra using nonreturn to zero (NRZ) formatting and staggeredManchester formatting.

FIG. 6 is a graph of the CDMA channel capacity as a function of thesignal to noise (SNR) margin.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the invention is described with reference to thefigures using reference designations as shown in the figures. Referringto FIG. 1, a code division multiple access (CDMA) transmitter provides atransmitted communication signal having a dual spectrum over first andsecond sets of communications channels. The dual spectrum is consideredas a composite spectrum having first and second spectra. In thepreferred form, the first spectrum is a split spectrum having a centernull in the communications bandwidth and the second spectrum is anonsplit spectrum having a center peak in the communications bandwidth.The communication signal transmitted by the transmitter is a dualspectrum signal communicated over the null-to-null communicationsbandwidth.

The first set of communication channels communicate a first N1 set ofdata streams 10. A first data stream of the first set of N1 data streamsof user data is clocked through a first shift register 12 for providingfirst shifted user data. The first shifted user data is nonreturn tozero (NRZ) formatted by a first NRZ data formatter 14 for providingfirst NRZ formatted data. A first clock generator 16 is used forproviding a first data clock for clocking the first data stream throughthe first shift register 12 and through the NRZ data formatter 14. Theclock generator 16 also provides a first code clock to a first CMDA codegenerator 18 for feeding a spreading code to a NRZ code formatter 20 forproviding an NRZ spreading code. The NRZ formatted spreading codemodulates the first NRZ formatted data using a first spreading mixer 22for providing a NRZ spread spectrum signal to a first modulator 24.

For each of the data streams 10, there is a respective first shifter 12,first NRZ data formatter 14, first CDMA code generator 18, first NRZcode formatter 20, first spreading mixer 22, and first modulator 24, ofa first communication channel in the first set of communicationchannels. The clock generator 16 communicates the first data clocksignal to all of the first shifters 12 and all of the first NRZ dataformatters 14, and communicates the first code clock signal to all ofthe first CDMA code generators 18 and the NRZ code formatters 20, forsynchronized communications.

The second set of communication channels communicate a second N2 set ofdata streams 26. A second data stream of the second set of N2 datastreams 26 of user data is clocked through a second shift register 28for providing second shifted user data. The second shifted user data isalso nonreturn to zero (NRZ) formatted by a second NRZ data formatter 30for providing second NRZ formatted data. A second clock generator 32 isused for generating a second data clock for clocking the second datastream of the N2 data streams 26 through a second shift register 28 andthrough a second NRZ data formatter 30. The second clock generator 32also provides a second code clock to a second CMDA code generator 34 forfeeding a second spreading code to a staggered Manchester code formatter36 for providing a staggered Manchester formatted spreading code. Thestaggered Manchester formatted spreading code modulates the second NRZformatted data using a second spreading mixer 38 for providing a splitspectrum spread signal to a second modulator 40.

For each of the N2 data streams 26, there is a respective second shifter28, second NRZ data formatter 30, second CDMA code generator 34,staggered Manchester code formatter 36, second spreading mixer 38, andsecond modulator 40, of a second communication channel in the second setof communication channels. The second clock generator 32 communicatesthe second data clock signal to all of the second shifters 28 and to allof the second NRZ data formatters 30, and communicates a second codeclock signal to all of the second CDMA code generators 34 and to all ofthe second staggered Manchester code formatters 36, for synchronizedcommunications.

The first set of data streams 10 and second set of data streams 26 areprocessed through respective communication channels. However, each ofthe spreading codes of all of the channels is different for cochannelisolation. The clock generators 16 and 32 can be one clock generator forproviding the same clock signals to the first and second sets ofcommunications channels. Additionally, the first set of data streams 10are data formatted and then modulated by NRZ formatted spreading codesfrom the first set NRZ code formatters 20, and the second set of datastreams 26 are data formatted and then modulated by Manchester formattedspreading codes from the Manchester formatters 36. The first set ofmodulators 24 and the second set of modulators 40 provide respective NRZspectrum spread signals and Manchester spectrum spread signals to atransmitter combiner 42 for combining the NRZ formatted spectrum spreadsignals and Manchester spectrum spread signals into a composite spectrumsignals having a dual spectrum. The NRZ formatted spectrum is a nonsplitspectrum and the Manchester formatted spectrum is a split spectrum.Hence, the composite spectrum is a composite of a nonsplit spectrumresulting for NRZ code formatting and a split spectrum resulting fromManchester code formatting. The modulators 24 and 40 uniphase modulate acarrier signal having a carrier frequency. Uniphase modulation isdefined as modulating one and only one phase on the carrier, which iseither the inphase phase of the carrier or the quadrature phase of thecarrier, but not both. The composite spread spectrum communicationsignal is a uniphase composite spread spectrum communication signal thatis amplified by a high power amplifier 44 and transmitted as a dualspectrum communication signal using a transmitter antenna 46.

Referring to FIGS. 1 and 2, and more particularly to FIG. 2, a dualspectrum CDMA receiver receives the split and nonsplit compositespectrum communication signal as a received communication signal using areceiver antenna 48. The received communication signal is amplified by alow noise amplifier 50 and spectrum despread by a despreading mixer 52.A clock generator 54 is used for providing a receiver clock signal. Theclock generator 54 generates a receiver code clock signal matching thecode clock signal generated in the transmitter. The clock generator 54also generates data clock signals for formatting and data detection. Inone form of the invention, a user control 57 is used for selecting thetype of code formatting. In the preferred form, NRZ and staggeredManchester code formatting is respectively used for formatting the firstand second sets of spreading codes. For a particular channel, and hence,for a particular CDMA code, the received communication signal isdespread using a spreading code formatter corresponding to one of theNRZ or staggered Manchester code formatters 20 or 36 used to spectrumspread one of the formatted data streams 10 or 26 in the transmitter.The user control 57 controls the selection of the code format. Aselectable NRZ or staggered Manchester formatter 58 is selectable to beeither an NRZ code formatter or a staggered Manchester code formatterand is clocked using the code clock signal from the clock generator 54.

A receiver CDMA code generator 56 generates a replica spreading code forthe respective communication channel. The replica spreading code and thecode formatter 58 in the receiver are identical to the spreading codeand the code formatter used in the transmitter for the samecommunication channel. The CDMA code generator 56 generates a CDMA codethat is fed to the receiver code formatter 58 for providing a formattedcode to the despreading mixer 52 that then despreads the communicationsignal for providing a despread signal. The despread signal iscommunicated to a conventional code and carrier tracking loop 60. Thecode tracking loop 60 provides a clock error signal to the clockgenerator 54 for adjusting clock timing for the despreading code formaintaining code tracking. The carrier tracking loop 60 provides acarrier replica to a carrier demodulator 62 for demodulating thedespread communication signal into a carrier demodulated data stream.The carrier demodulated data stream from carrier demodulator 62 is fedto a bit synchronizer 64 generating a bit timing signal that is fed to adata detector 66 for synchronized clocking of the demodulated datastream into a replica data stream 68. Bit timing may also be generatedfrom the tracking loop 60. The data clock signal from the clockgenerator 54 is received by the data detector 66 for synchronizing thereplica data stream 68. The replica data stream 68 is a replica of thedata stream 10 or 26 spectrum spread by the spreading code. In thismanner, the receiver can be used to receive either an NRZ or a staggeredManchester code formatted CDMA signal of the composite communicationsignal respectively having either a nonsplit spectrum or a splitspectrum.

The preferred form of the receiver is a code format selectable receiver.The transmitter can be adapted to change the code format for arespective channel by feeding a data stream into either an NRZ orstaggered Manchester code formatted communication channel. However, itshould be apparent that the receiver could be a fixed code formatreceiver using either NRZ or staggered Manchester code formatting, butnot both, without the use of the user control 57, and without aselectable formatter 58. The formatter 58 is then either a fixed NRZ ora fixed staggered Manchester code formatter. In either case, the datastreams can have the same data formatting, such as NRZ data formattingby NRZ data formatters 14 and 30.

Referring to FIGS. 3 and 4, Manchester and staggered Manchester codesymbol waveforms are respectively shown for showing that the staggeredManchester code symbol waveform is a replica of the original Manchestercode symbol waveform but staggered, that is, shifted, in time by aquarter of the code symbol time τ. The staggered Manchester codeformatting is done by staggering the underlying square wave signal by aquarter of the square wave cycle compared to the underlying square waveof the Manchester formatted code signal. As a result of this staggering,the first quarter of the square symbol gets moved to the last quarter ofthe square wave symbol as shown in the FIG. 4. It can also be seen fromthis figure that the antisymmetry in the waveform shape between thefirst and the second half of the code symbol with a Manchester codeformat is changed in the case of staggered Manchester code format to asymmetrical relationship between the two halves of the code symbolwaveform.

Referring to all other Figures and more particularly to FIGS. 5 and 6,the communication channel signals using NRZ code formatting or staggeredManchester code formatting have respective nonsplit and split spectraoccupying the same null-to-null communication bandwidth, that may be,for example, 200 kHz with a data rate of 400 bps. The code chipping ratefor the NRZ code formatter in a CDMA system may be a 100 kHz chippingrate for providing the null-to-null bandwidth for the NRZ code formattedCDMA signal. With only NRZ code formatted CDMA signaling, the capacityof fifty CDMA channels is achieved with an available link margin of 6.0dB at a BER of 10⁻⁵. Under the same conditions, but with added staggeredManchester code format signaling at 50.0 kHz, for producing a dualspectrum CDMA signal, the overall channel capacity is increased. Thecommunication channel has overlapping nonsplit and split spectrarespectively provided by the NRZ code formatting and staggeredManchester code formatting. The total channel capacity is the sum of theNRZ code formatted channels and the staggered Manchester code formattedchannels. The sum total is improved to sixty nine channels, which is a38% improvement in the channel capacity over a conventional CDMA systemusing only NRZ code formatting generating a nonsplit spectrum.

Power spectral densities for the NRZ and staggered Manchester codeformatted signals, filtered with a 6th order Butterworth filter have acutoff of 100 kHz, as is shown in FIG. 5. A 19% to 48% capacityimprovement is practicable using a combination of NRZ code formattingand staggered Manchester code formatting within a given frequencybandwidth for link margins of 3-12 dB. With a modest increase in CDMAsystem complexity, a CDMA system can obtain increased channel capacityusing different code formatters for providing different overlappingpower spectral densities within the null-to-null communicationbandwidth. In the preferred form, NRZ code formatting generates nonsplitspectra, and, staggered Manchester code formatting generates splitspectra of the dual spectrum CDMA communication signal.

The present invention is directed to a dual spectrum CDMA communicationsystem using two different code formats for providing respective spectraoverlapping within a communication bandwidth. The respective spectrashare the same bandwidth with minimal cross interference due to onespectrum having a center peak and the other spectrum having peaks awayfrom the center, for effective bandwidth sharing within the samecommunications bandwidth. The dual spectrum CDMA communication systemoffers increased channel capacity. It should now be apparent that a mixof transmitters and receivers could operate as part of a completecommunication system communicating both split and nonsplit spectrumsignals. For example, one group of transmitters or satellites couldtransmit split spectrum signals while another group of transmitters orsatellites could transmit nonsplit spectrum signals, all of the signalscommunicating within the same CDMA communications bandwidth. Thoseskilled in the art can make enhancements, improvements, andmodifications to the invention, and these enhancements, improvements,and modifications may nonetheless fall within the spirit and scope ofthe following claims.

1. A system for communicating a first formatted data stream and a secondformatted data stream through a dual spectrum signal over acommunication bandwidth, the system comprising, a first code formatterfor formatting a first spreading code into a first formatted code, afirst spreader for spectrum spreading the first formatted data stream bythe first formatted code into a first spread spectrum signal, a secondcode formatter for formatting a second spreading code into a secondformatted code, a second spreader for spectrum spreading the secondformatted data stream by the second formatted code into a second spreadspectrum signal, and a modulator for combining and communicating thefirst spread spectrum signal and the second spread spectrum signal intothe dual spectrum signal, the first spread spectrum signal having afirst spectrum over the communication bandwidth and the second spreadspectrum signal having a second spectrum over the communicationbandwidth, the first spread spectrum signal and the second spreadspectrum signal respectively uniphase modulating a carrier, the dualspectrum signal being a uniphase dual spectrum signal, wherein, thefirst code formatter is an NRZ code formatter, and the second codeformatter is a staggered Manchester code formatter.
 2. The system ofclaim 1 wherein, the first spectrum is a nonsplit spectrum with a peakwithin the communication bandwidth, and the second spectrum is a splitspectrum with a null within the communication bandwidth.
 3. The systemof claim 1 wherein the system is a code division multiple access system.4. The system of claim 1 having a first receiver for spread spectrumdespreading the first spread spectrum signal and the second spreadspectrum signal, the first receiver comprising, a first replica codeformatter for formatting a first replica spreading code into a firstreplica formatted code, the first replica spreading code being a replicaof the first spreading code, and a first despreader for spectrumdespreading the first spread spectrum signal by the first replicaformatted code into a first despread signal.
 5. The system of claim 1having a second receiver for spread spectrum despreading the secondspread spectrum signal and the second spread spectrum signal, the secondreceiver comprising, a second replica code formatter for formatting asecond replica spreading code into a second replica formatted code, thesecond replica spreading code being a replica of the second spreadingcode, and a second despreader for spectrum despreading the second spreadspectrum signal into a second despread signal.
 6. The system of claim 1further having a first receiver and a second receiver, the firstreceiver comprising, a first replica code formatter for formatting afirst replica spreading code into a first replica formatted code, thefirst replica spreading code being a replica of the first spreadingcode, and a first despreader for spectrum despreading the first spreadspectrum signal into a first despread signal, and a detector fordetecting the first formatted data stream for the first despread signal,and the second receiver comprising, a second replica code formatter forformatting a second replica spreading code into a second replicaformatted code, the second replica spreading code being a replica of thesecond spreading code, and a second despreader for spectrum despreadingthe second spread spectrum signal by the second replica formatted codeinto a second despread signal.
 7. The system of claim 1 furthercomprising, a first replica code formatter for formatting a firstreplica spreading code into a first replica formatted code, the firstreplica spreading code being a replica of the first spreading code, afirst despreader for spectrum despreading the first spread spectrumsignal into a first despread signal, a second replica code formatter forformatting a second replica spreading code into a second replicaformatted code, the second replica spreading code being a replica of thesecond spreading code, and a second despreader for spectrum despreadingthe second spread spectrum signal into a second despread signal,wherein, the first code formatter is an NRZ formatter, the first spreadspectrum signal is a nonsplit spectrum signal, the first spectrum is anonsplit spectrum having a center peak, the second code formatter is astaggered Manchester formatter, the second spread spectrum signal is asplit spectrum signal, the second spectrum is a split spectrum having acenter null, the first replica code formatter is an NRZ formatter, andthe second replica code formatter is a staggered Manchester codeformatter.
 8. The system of claim 1 further comprising, a first replicacode formatter for formatting a first replica spreading code into afirst replica formatted code, the first replica spreading code being areplica of the first spreading code, a first despreader for spectrumdespreading the first spread spectrum signal into a first despreadsignal, a second replica code formatter for formatting a second replicaspreading code into a second replica formatted code, the second replicaspreading code being a replica of the second spreading code, and asecond despreader for spectrum despreading the second spread spectrumsignal into a second despread signal, wherein, the first code formatteris in a transmitter, the first spread spectrum signal is a nonsplitspectrum signal, the second code formatter is in the transmitter, thesecond spread spectrum signal is a split spectrum signal, the firstreplica code formatter is in a first receiver, the second replica codeformatter is in a second receiver, the first formatted data stream iscommunicated between the transmitter and the first receiver, and thesecond formatted data stream is communicated between the transmitter andthe second receiver.
 9. The system of claim 1 further comprising, afirst replica code formatter for formatting a first replica spreadingcode into a first replica formatted code, the first replica spreadingcode being a replica of the first spreading code, a first despreader forspectrum despreading the first spread spectrum signal into a firstdespread signal, a second replica code formatter for formatting a secondreplica spreading code into a second replica formatted code, the secondreplica spreading code being a replica of the second spreading code, anda second despreader for spectrum despreading the second spread spectrumsignal into a second despread signal, wherein, the first code formatteris an NRZ formatter, the first spread spectrum signal is a nonsplitspectrum signal, the second code formatter is a staggered Manchesterformatter, the second spread spectrum signal is a split spectrum signal,the first replica code formatter is an NRZ formatter, the second replicacode formatter is a staggered Manchester code formatter, the first codeformatter and the second code formatter are disposed in a transmitter.10. The system of claim 1 wherein, the staggered Manchester format is astaggered Biphase-L format.
 11. The system of claim 1 wherein, thestaggered Manchester format is a staggered binary offset carrier format.12. A system for communicating a first formatted data stream and asecond formatted data stream through a dual spectrum signal over acommunication bandwidth, the system comprising, a first code formatterfor formatting a first spreading code into a first formatted code, afirst spreader for spectrum spreading the first formatted data stream bythe first formatted code into a first spread spectrum signal, a secondcode formatter for formatting a second spreading code into a secondformatted code, a second spreader for spectrum spreading the secondformatted data stream by the second formatted code into a second spreadspectrum signal, and a modulator for combining and communicating thefirst spread spectrum signal and the second spread spectrum signal intothe dual spectrum signal, the first spread spectrum signal having afirst spectrum over the communication bandwidth and the second spreadspectrum signal having a second spectrum over the communicationbandwidth, the first spread spectrum signal and the second spreadspectrum signal respectively modulating only one phase of a carrier, thedual spectrum signal being a uniphase dual spectrum signal, wherein, thefirst code formatter is an NRZ code formatter, the second code formatteris a staggered Manchester code formatter, the uniphase modulation of thecarrier being defined as modulating one phase of the carrier by onesingle signal being the first spread spectrum signal into a firstuniphase modulated signal, the uniphase modulation of the carrier beingdefined as modulating one phase of the carrier by one single signalbeing the second spread spectrum signal into a second uniphase modulatedsignal, and the dual spectrum signal being a combination of the firstuniphase modulated signal and the second uniphase modulated signal whencombined, the first uniphase modulated signal and the second uniphasemodulated signal both modulating only one phase of the carrier.
 13. Thesystem of claim 12 wherein, the first code formatter is an NRZ codeformatter, and the second code formatter is a staggered Manchester codeformatter.
 14. A system for communicating a first formatted data streamand a second formatted data stream through a dual spectrum signal over acommunication bandwidth, the system comprising, a first code formatterfor formatting a first spreading code into a first formatted code, afirst spreader for spectrum spreading the first formatted data stream bythe first formatted code into a first spread spectrum signal, a secondcode formatter for formatting a second spreading code into a secondformatted code, a second spreader for spectrum spreading the secondformatted data stream by the second formatted code into a second spreadspectrum signal, and a modulator for modulating only one phase of thecarrier by only the first spread spectrum signal for providing a firstmodulated signal and for modulating the same phase of the carrier byonly the second spread spectrum signal for providing a second modulatedsignals, and a combiner for combining the first modulated signal and thesecond modulated signal into the dual spectrum signal, the dual spectrumsignal being a carrier modulated signal having only one carrier phasemodulated, the first modulated signal from the first spread spectrumsignal having a first spectrum over the communication bandwidth, thesecond modulated signal from second spread spectrum signal having asecond spectrum over the communication bandwidth.
 15. The system ofclaim 14 wherein, the first code formatter is an NRZ code formatter, andthe second code formatter is a staggered Manchester code formatter.